Quantitative structure-activity studies on monoamine oxidase inhibitors

Monoamine Oxidase (MAO) as a Potential Target for Anticancer Drug Design and Development

Monoamine oxidases (MAOs) are oxidative enzymes that catalyze the conversion of biogenic amines into their corresponding aldehydes and ketones through oxidative deamination. Owing to the crucial role of MAOs in maintaining functional levels of neurotransmitters, the implications of its distorted activity have been associated with numerous neurological diseases. Recently, an unanticipated role of MAOs in tumor progression and metastasis has been reported. The chemical inhibition of MAOs might be a valuable therapeutic approach for cancer treatment. In this review, we reported computational approaches exploited in the design and development of selective MAO inhibitors accompanied by their biological activities. Additionally, we generated a pharmacophore model for MAO-A active inhibitors to identify the structural motifs to invoke an activity.

Privileged scaffolds as MAO inhibitors: Retrospect and prospects

This review aims to be a comprehensive, authoritative, critical, and readable review of general interest to the medicinal chemistry community because it focuses on the pharmacological, chemical, structural and computational aspects of diverse chemical categories as monoamine oxidase inhibitors (MAOIs). Monoamine oxidases (MAOs), namely MAO-A and MAO-B represent an enormously valuable class of neuronal enzymes embodying neurobiological origin and functions, serving as potential therapeutic target in neuronal pharmacotherapy, and hence we have coined the term "Neurozymes" which is being introduced for the first time ever. Nowadays, therapeutic attention on MAOIs engrosses two imperative categories; MAO-A inhibitors, in certain mental disorders such as depression and anxiety, and MAO-B inhibitors, in neurodegenerative disorders like Alzheimer's disease (AD) and Parkinson's disease (PD). The use of MAOIs declined due to some potential side effects, food and drug interactions, and introduction of other classes of drugs. However, curiosity in MAOIs is reviving and the recent developments of new generation of highly selective and reversible MAOIs, have renewed the therapeutic prospective of these compounds. The initial section of the review emphasizes on the detailed classification, structural and binding characteristics, therapeutic potential, current status and future challenges of the privileged pharmacophores. However, the chemical prospective of privileged scaffolds such as; aliphatic and aromatic amines, amides, hydrazines, azoles, diazoles, tetrazoles, indoles, azines, diazines, xanthenes, tricyclics, benzopyrones, and more interestingly natural products, along with their conclusive SARs have been discussed in the later segment of review. The last segment of the article encompasses some patents granted in the field of MAOIs, in a simplistic way.

Selective inhibitors of monoamine oxidase (MAO). 5. 1-Substituted phenoxathiin inhibitors containing no nitrogen that inhibit MAO A by binding it to a hydrophobic site

It is believed that a monoamine oxidase (MAO) inhibitor specific for MAO A, which is reversibly bound to this enzyme and displaceable by tyramine, will be an antidepressant which will not cause a rise in blood pressure when tyramine-containing foods are ingested. Some linear tricyclic compounds with a larger and a smaller group forming the central ring and with a lipophilic group ortho to the larger group (here mostly the SO2 function of phenoxathiin 10,10-dioxide) are reported to have the sought properties. Potency appears to require short length and relatively small cross section for the substituent. The 1-ethyl (13), 1-vinyl (22), 1-trifluoromethyl (27), and 1-iodo (76) phenoxathiin dioxides had the best profiles. Structure-activity relationships, syntheses, and a possible rationale for the selectivity of these compounds and related tricyclics are given. Compound 13 was selected for further development. A summary of pharmacological data for 13 is given.

QSAR analysis of indole analogues as monoamine oxidase inhibitors

The quantitative structure-activity relationship (QSAR) analysis with comparative molecular field analysis (CoMFA) of indole derivatives-monoamine oxidase (MAO) inhibitors were done. The pharmacophore model included four features: two hydrophobic rings, one donor atom, and one acceptor site. The predictive values (cross-validated r2) of QSAR analysis for the inhibition of MAO-A and MAO-B were 0.743 and 0.603, respectively. The contributions of steric and electrostatic fields in the interaction between inhibitors and enzymes were equal. The three-dimensional arrangement of these fields for MAO-A and MAO-B suggests that structures of active site for both enzymes are considerably differed from each other.

Inhibition of rat liver mitochondrial monoamine oxidase by hydrazine-thiazole derivatives: structure-activity relationships

The purpose of this research is to study the relationship between chemical structure and inhibitory activity of some hydrazine-thiazole derivatives on rat liver mitochondria monoamine oxidase (MAO). Forty-five compounds belonging to three series of hydrazine-thiazole derivatives, with either alkylic or arylic substituents in the thiazole ring, were tested. The highest inhibitory activity was observed with piperonyl derivatives 25 and 40, which contain a 4-methyl group in the thiazole nucleus. The structure-activity relationship of MAO inhibitors was established in relation to hydrophobic, electronic and steric hindrance parameters. A mechanism of enzyme inhibition was proposed based on the calculation of HOMO energies.

Correlation between monoamino oxidase inhibitor activity of some thiazol-2-ylhydrazines and their interaction with dipalmitoylphosphatidylcholine liposomes

A calorimetric investigation has been carried out on the influence exerted by some 1-(alkoxybenzoyl)-2-(4-substituted thiazolyl-2-yl)hydrazines, possessing monoamine oxidase inhibitory (MAOI) activity, on the thermotropic behavior of model membranes constituted by dipalmitoylphosphatidylcholine (DPPC) vesicles. Attention was paid to evaluate how structural variations of drugs may influence drug-lipid interaction. The examined drugs were found to modify the gel to liquid-crystal phase transition of DPPC liposomes, by causing a shift of the transition temperature (Tm) toward lower values and a negligible variation in the enthalpy changes (delta H). The different effects on DPPC thermotropic behavior of these MAOI drugs could be considered in terms of different substituents on the molecule's backbone. The calorimetric results were related to drug's MAO inhibitory activity measured by fluorescence techniques and the apparent distribution coefficient of the compounds in water/n-octanol. A hypothesis on a correlation between a drug's structure, inhibitory activity, and membrane interaction has been suggested.

Inhibition of rabbit liver monoamine oxidase by nitro aromatic compounds

Nitrobenzoid, nitroheterocyclic and cyanobenzoid compounds inhibit type B monoamine oxidase. A partially purified enzyme preparation from rabbit liver mitochondria, oxidizing rho-dimethyl-aminobenzylamine as the substrate, was competitively inhibited by nitrobenzoid compounds with K1 values in the range of 0.28 muM for rho-dinitrobenzene to 0.56 muM for rho-nitrobenzoic acid. The potencies of nitrobenzoid compounds were positively correlated with the Hammett sigma value for each substituent on nitrobenzene. Dinitro derivatives were slightly more potent than the corresponding mononitro compounds but not as potent as would be expected from their sigma values. For the nitroheterocyclic compounds, inhibition was also competitive; the lowest K1 was 1.3 muM for 5-nitrofurfural semicarbazone (nitrofurazone). Compounds with cyano groups in place of nitro groups were also inhibitory; the most potent was rho-acetobenzonitrile with a K1 of 1.3 muM. The results of this study indicate that, in addition to nitrobenzoid compounds, other compounds with planar, electron-deficient nuclei are effective inhibitors of type B monoamine oxidase. Although hydrophobic and steric parameters may play some role in inhibition, the predominant factor is the electron-withdrawing power of the ring substituents.